The real-time FFT is the ideal tool for visualization of comb filters and narrow band effects. It measures the actual level and the averaged level Leq in three ranges over the entire audio band. The optional Extended Acoustic Pack offers an additional high-resolution Zoom-FFT up to 0.4 Hz steps in the frequency range 5 Hz - 20 kHz and adds the linear audio recording (24 Bit, 48 kHz). The Spectral Limits Option extends the FFT Analysis with trace capturing, relative curve display and comprehensive tolerance handling.
RT60 Reverberation Time
The XL2 measures the energy decay in the range from 63 Hz to 8 kHz by the Schroeder method in 1/1 octave bands. Automatic triggering and averaging of multiple measurements simplifies the operation and minimizes the measurement time. Use either an impulse source or an interrupted pink noise as the test signal. The optional Extended Acoustic Pack extends the RT60 measurement to a 1/3 octave resolution.
For a stereo sound image, it is important to match the polarities of the left and right speakers. The XL2 measures the polarity of cables, single speakers and speaker cabinets. The detailed result page displays the measured polarity as octave bands from 125 Hz to 8 kHz. This allows in-depth verification of the polarity - frequency relation. The polarity test signal is provided by the NTi Audio Test CD or the Minirator test signal generator.
The delay function supports the accurate setup of delay lines and thus the optimization of the directionality of the signal source. The XL2 measures the delay time between the electrical reference signal and the acoustic signal from the speaker. The required delay settings are displayed automatically, allowing the audio engineer to set the measured delay time directly into the delay device in the rack.
Speech Intelligibility STIPA (optional)
The XL2 Analyzer measures speech intelligibility according to the latest revision of standard IEC 60268-16:2011 (edition 4) as well as older revisions. It offers ambient noise correction and automated averaging for consecutive measurements. The XL2 displays the measurement results as STI or CIS, accompanied by the individual levels and modulation indices of the seven octave bands.
The measurement results are acquired from the dedicated STIPA test signal source:
- NTi Audio TalkBox
Acoustic signal generator, required for audio systems that include voice microphones, allows the entire signal chain to be measured.
- Minirator MR-PRO
Test signal generator, required for audio systems with line inputs
- STIPA Test CD
1/12 Octave Band Analysis (optional)
The Spectral Limits Option extends the function range of the XL2 with a 1/6th and 1/12th octave RTA analyzer. The XL2 Analyzer compares spectral measurements against a tolerance band and shows exceptions in every frequency band. This passed/failed condition is further visualized by the limit button and forwarded to the I/O interface of the instrument in order to drive an external alarm device such the accessory Stack Light. The optional Extended Acoustic Pack adds the linear audio recording (24 Bit, 48 kHz).
Noise Curves (optional)
The noise curve measurement provides an objective rating of the background noise level in a room or environment. The noise curve rating of a spectrum is designated as the value of the highest noise curve “touched” by the measured octave-band spectrum. The speech interference level (SIL) and the noise curve rating are calculated in parallel. The Noise Curve function is offered with the Spectral Limits Option.
Supported noise curve measurements and standards:
- Noise Rating (NR)
in accordance with ISO 1996
- Noise Criteria (NC)
in accordance with ANSI 12.2-2008 and -1995
- Room Noise Criteria (RNC)
in accordance with ANSI 12.2-2008
- Room Criteria (RC)
in accordance with ANSI 12.2-1995
- Preferred Noise Criteria (PNC)
in accordance with ASA 1971